Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-05-01
2001-07-17
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090170
Reexamination Certificate
active
06260524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a valve timing control system for adjusting or controlling valve timing at which an intake valve and/or an exhaust valve of an internal combustion engine is opened and closed in dependence on operating state of the engine. More particularly, the present invention is concerned with a valve timing control system for an internal combustion engine which system is capable of controlling the valve timing such that an actual valve timing can speedily converge to a desired valve timing immediately after power-on of the engine or immediately upon restoration of engine operation state to a normal state from an abnormal state in which some abnormality has occurred in the engine operation state and which is further capable of suppressing overshoot of the actual valve timing, to thereby protect the operation performance of the engine against degradation while protecting the exhaust gas quality against deterioration with high reliability essentially without fail.
2. Description of Related Art
In the technical field of the internal combustion engine, a system for controlling variably the operation timing for at least one of an intake valve and an exhaust valve in dependence on the operation state of the internal combustion engine is well known. The valve timing control system of this type includes a mechanism for holding or controlling variably the valve timing in dependence on the engine operation state with a view to realizing an optimal valve timing control.
By way of example, the timing for opening the intake valve is held in an advanced phase when the engine rotation number is in a stable intermediate range for the purpose of realizing an EGR (Exhaust Gas Recirculation) function, whereas when the engine rotation number is in a higher speed range or in a lower speed range, the intake valve is held in a retarded phase in order to secure a high output torque or ensure a stable operation state.
In the following, referring to
FIGS. 10
to
31
, description will be made of the conventional valve timing control system for the internal combustion engine.
FIG. 10
is a schematic diagram showing generally a configuration of a gasoline engine system equipped with a conventional valve-timing regulating or controlling mechanism. Referring to the figure, an internal combustion engine denoted generally by reference numeral
1
constitutes a major part of the gasoline engine system and includes a plurality of cylinders (e.g. four cylinders). In
FIG. 10
, however, only one cylinder and associated components are illustrated representatively.
As is shown in
FIG. 10
, a cylinder block
2
forms a cylinder portion of the engine
1
. A cylinder head
3
is connected to the cylinder block
2
at a top end thereof. A piston
4
is housed within a cylinder chamber formed in the cylinder block
2
so as to move reciprocatively in the vertical direction. A crank shaft
5
is operatively coupled to the piston
4
at a bottom end thereof and caused to rotate in unison with the reciprocative motion of the piston
4
.
A crank angle sensor
6
which can be disposed, for example, in the vicinity of the crank shaft
5
is constituted by an electromagnetic pickup or sensor to serve for generating a crank angle signal SGT in synchronism with revolution of the engine
1
. The crank angle signal SGT is utilized not only for detecting the engine speed or engine rotation number NE (rpm) of the engine
1
but also for the detection that the crank shaft
5
is at a predetermined reference crank angle (° CA).
A signal rotor
7
is integrally mounted on the crank shaft
5
and has an outer peripheral surface formed with a pair of teeth
7
a
with an angular distance of 180° therebetween. The teeth
7
a
are formed of a magnetic material. Upon every passing of each tooth
7
a
in front of the crank angle sensor
6
, a pulse-like crank angle signal SGT is generated by the crank angle sensor
6
.
A combustion chamber
8
is defined by inner walls of the cylinder block
2
and the cylinder head
3
and a top wall of the piston
4
, respectively. Air-fuel mixture charged into the engine
1
undergoes combustion within the combustion chamber
8
. A spark plug
9
is disposed at the top of the cylinder head
3
so as to partially project into the combustion chamber
8
. The air-fuel mixture is fired by electric discharge taking place at the spark plug
9
.
A distributor
10
is installed, being coupled to an exhaust-side cam shaft
20
(described hereinafter) which is mounted on the cylinder head
3
for applying a high ignition voltage sequentially to the spark plugs
9
provided for the individual cylinders, respectively. To this end, an ignitor
11
is provided for generating the high firing voltage.
More specifically, each of the spark plugs
9
is electrically connected to the distributor
10
by way of a high-voltage rated cord (not shown), wherein the high voltage outputted from the ignitor
11
is distributed to the individual spark-plugs
9
, respectively, by means of the distributor
10
in synchronism with the rotation of the crank shaft
5
.
Further installed in association with the cylinder block
2
is a water temperature sensor
12
which serves for detection of a temperature W of cooling water flowing through a coolant passage. An intake port
13
is provided at an intake side of the cylinder head
3
while an exhaust port
14
is disposed at an exhaust side of the cylinder head
3
.
An intake passage
15
is communicated to the intake port
13
with an exhaust passage
16
being communicated to the exhaust port
14
. An intake valve
17
is disposed in the intake port
13
of the cylinder head
3
while an exhaust valve
18
is installed in the exhaust port
14
of the cylinder head
3
.
An intake-side cam shaft
19
is disposed above the intake valve
17
for driving the intake valve
17
to the open or close state. Similarly, the exhaust-side cam shaft
20
is disposed above the exhaust valve
18
for opening or closing the exhaust valve
18
.
An intake timing pulley
21
is mounted on the intake-side cam shaft
19
at one end thereof, while an exhaust timing pulley
22
is mounted on the exhaust-side cam shaft
20
at one end thereof. The intake timing pulley
21
and the exhaust timing pulley
22
are operatively coupled to the crank shaft
5
by means of a timing belt
23
so that each of the cam shafts
19
and
20
can rotate at a speed substantially equal to a half of the rotation speed of the crank shaft
5
.
When the engine
1
is in the operating state, the driving torque of the crank shaft
5
is transmitted to the cam shafts
19
and
20
, respectively, by way of the timing belt
23
and the timing pulleys
21
and
22
to thereby rotate the cam shafts
19
and
20
, respectively.
Thus, the intake valve
17
and the exhaust valve
18
are driven, respectively, to the open/close states in synchronism with the rotation of the crank shaft
5
and hence the vertical reciprocative motion of the piston
4
. In other words, each of the intake valve
17
and the exhaust valve
18
is driven with a predetermined open/close timing in synchronism with a series of four strokes, i.e., suction stroke, compression stroke, explosion (expansion) stroke and exhaust stroke of the engine
1
.
A cam angle sensor
24
is disposed in the vicinity of the intake-side cam shaft
19
and designed to generate a cam angle signal SGC for detecting the actuation timing (i.e., valve timing) of the intake valve
17
.
A signal rotor
25
is integrally mounted on the intake-side cam shaft
19
, wherein the outer peripheral surface of the signal rotor
25
is formed with four teeth
25
a
at an angular distance of 90° therebetween. Each of the teeth
25
a
is formed of a magnetic material. Every time each of the teeth
25
a
passes in front of the cam angle sensor
24
, a pulse-like cam angle signal (pulse signal indicating the angular position of the cam) SGC is generated by the cam angle sensor
24
.
A throttle valve
26
is installed in th
Lo Weilun
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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